Over the course of years, a wide variety of hinges for automatically closing doors have been developed. U.S. Pat. No. 165,619 discloses a self-closing hinge for a gate which includes cams so shaped that as the gate is opened, an upper cam which is attached to the gate rides upwardly on a lower cam which is attached to the gatepost. Gravity then provides the restoring force for returning the gate to closed position. The patent also shows a flat having a small depression therein for providing a dwell so that if the gate is open far enough the gate will remain open until it is partially closed by hand. U.S. Pat. No. 571,133 discloses a spring hinge utilizing a coil spring for returning the spring to closed position. However, the spring is used in torsion, a method of use which has the disadvantage of shortening the life of the spring.
U.S. Pat. No. 3,518,716 shows a hinge in which a cam moves vertically within a housing and is locked thereto for rotation therewith by contact between flat regions on each of the cam and the housing. However, wear soon decreases the efficacy of this locking means. In addition, wear takes place between a coil spring and a pin passing therethrough.
While the general principles of self-closure, cam action and a dwell are known, substantial disadvantages have been present in conventional structures, these disadvantages being the aforenoted shortened life of a spring member used in torsion, relative axial motion of the spring halves which results in an undesired vertical motion of a door equipped with such a hinge and the requirement for different hinge structures for left and right mounted doors. As is evident, a hinge structure which avoids such disadvantages is greatly to be desired.